Solar still innovations for sustainable water desalination: recent advances, performance enhancement strategies, and future perspectives
Abstract
Solar stills provide a simple, low-energy option for decentralized desalination, but low freshwater yield, intermittent solar input, and thermal losses continue to limit wider deployment. This critical narrative review evaluates solar-still configurations, heat- and mass-transfer mechanisms, thermal-energy storage, material modifications, and hybrid energy-supply strategies using a common framework that considers productivity, auxiliary-energy demand, operational complexity, maintenance, cost, durability, and life-cycle implications. The evidence shows that reported percentage improvements cannot reliably rank technologies because baseline design, irradiance, climate, water depth, reference area, operating duration, and system boundaries vary widely among studies. Low-complexity passive measures, including improved insulation, absorber geometry, wetting, and condensation management, are the most deployment-ready options, while basin-integrated phase-change-material storage is the most promising advanced approach for extending production beyond peak sunshine with moderate added complexity. Nano-enhanced phase-change materials, nanofluids, multi-effect, PV/T, and externally coupled hybrid systems can provide further gains, but their practical superiority remains uncertain because of auxiliary-energy use, cost, material stability, fouling, corrosion, containment, and maintenance requirements. Major evidence gaps include poor cross-study comparability, limited seasonal and long-term outdoor validation, incomplete uncertainty and energy accounting, insufficient durability data, and inconsistent verification of product-water quality. Future research should prioritize standardized side-by-side testing, absolute yield and complete energy reporting, repeatability and uncertainty analysis, seasonal durability assessment, verified water quality, levelized cost of water, and life-cycle evaluation. A multilayer-absorber–metallic-wire-sponge configuration is proposed as a testable hypothesis requiring matched experimental validation before performance synergy is claimed.